PUCCH Power Control Among LTE Systems
Only transmission of a Physical Uplink Control Channel (PUCCH) on a Primary Component Carrier (PCC) is supported in a Long Term Evolution (LTE) system. PUCCH transmit power is adjusted in each transmission sub-frame according to a corresponding uplink Transmit Power Control (TPC) command which can be obtained in the following two approaches:
In a first approach, the TPC command is obtained from a TPC field in a Physical Downlink Control Channel (PDCCH), or an Enhanced PDCCH, corresponding to the PCC, using the Downlink Control Information (DCI) format 1A/1B/1D/1/2A/2/2B/2C/2D and scrambled with a Cell-Radio Network Temporary Identifier (C-RNTI).
In a second approach, the TPC command is obtained from a PDCCH or an EPDCCH, transmitted in a Common Search Space (CSS) of a PCC, using the DCI format 3/3A and scrambled with a TPC-PUCCH-RNTI. This approach is a TPC multicast approach in which uplink TPC commands of a plurality of User Equipments (UEs) can be transmitted in the same PDCCH, and each of the UEs obtains its own uplink TPC command in the TPC multicast command according to a Transmit Power Control-index (TPC-index) preconfigured by an higher layer.
When the UE detects both of the PDCCHs transmitted in the two approaches above, the UE adjusts the power according to the uplink TPC command in the PDCCH obtained in the first approach.
Carrier Aggregation
Carrier Aggregation (CA) has been introduced to the Long Term Evolution-Advanced (LTE-A) system so that a plurality of consecutive or inconsecutive carriers served by the same evolved Node B (eNB) are aggregated together to serve the UE concurrently. These carriers aggregated together are referred to as Component Carriers (CCs). Each cell can be a component carrier, and cells (component carriers) served by different eNBs cannot be aggregated. The bandwidth of each carrier cannot go beyond 20 MHz for back compatibility with an LTE UE.
One of the component carriers aggregated for the UE is defined as a Primary Component Carrier (PCC), and the other component carriers are referred to as Secondary Component Carriers (SCCs).
Carrier aggregation of a Frequency Division Duplex (FDD) carrier and a Time Division Duplex (TDD) carrier may be supported in an evolved system subsequent to the LTE-A system. Since the FDD carrier operates in a different operating mode from the TDD carrier, a new uplink Acknowledge/Negative Acknowledge (ACK/NACK) transmission solution may be introduced, that is:
The eNB groups aggregated downlink carriers into N sets Si of downlink carriers so that a downlink carrier belongs to only one set of downlink carriers, and carriers in a set of downlink carriers operates in the same duplex mode. All of TDD carriers in a set of carriers operate in the same TDD uplink/downlink configuration.
The eNB configures an uplink carrier CUL,i for the set Si of downlink carriers so that the uplink carrier CUL,i operates in the same duplex mode as the set of downlink carriers. If the downlink carriers are TDD carriers, then the uplink carrier operates in the same TDD uplink/downlink configuration as the corresponding set of downlink carriers. There are different uplink carriers corresponding to different sets of downlink carriers.
ACK/NACK information corresponding to downlink data received in the set Si of downlink carriers is transmitted in a PUCCH on the uplink carrier CUL,i.
There has been absent a corresponding solution to transmission of an uplink power control command when the UE supports transmission of PUCCHs on different uplink carriers corresponding to different sets of carriers.